1. Field of the Invention
The present invention relates to a lead frame with a pre-mold paddle for a semiconductor chip package and, more particularly, to an improved lead frame with a pre-mold paddle for a semiconductor chip package, which can prevent delamination and cracking between a mold body and the paddle on which a semiconductor chip is placed, in the semiconductor chip package.
2. Discussion of the Related Art
Referring to FIG. 1, the lead frame, a metal structure used in fabrication of the semiconductor chip package, includes in general guide rails 10 on both side of the lead frame 1a for supporting the lead frame 1a itself and guiding the lead frame 1a in the automatic transfer of the lead frame 1a during fabrication and a paddle 11 disposed at the center thereof for supporting the semiconductor chip 5. The lead frame 1a further includes inner leads 2, each for electrical connection to a bonding pad, a wire 12 which provides an external connection terminal for the semiconductor chip 5, and outer leads 13 which extend outside of the inner leads 2. A dam bar 14 is provided between the inner lead 2 and the outer lead 13 for supporting the inner lead 2 and the outer lead 13. The dam bar 14 is removed by trimming after the application of the EMC (Epoxy Molding Compound) molding. The paddle 11 is supported and connected to the body of the lead frame 1a by support bars 4a, and there are gaps between the inner leads 2 and the paddle 11.
However, in the aforementioned conventional lead frame 1a, the molded body 8 enclosing the semiconductor chip 5 and the paddle 11 is made of an EMC, whereas the paddle 11, which occupies the largest area of the lead frame 1a, made is of a copper alloy which is the same material as other elements but different from that of the molded body. Thus, the thermal coefficients of the molded body and the paddle are different from each other considering their properties. Because of this there is the problem of delamination, which is a separation of the close bonding between the bottom of the paddle 11 and the mold body 8 caused by shearing due to a difference in the thermal expansion coefficients between them during the packaging process, aging conducted after completion of the packaging, heat treatment for reliability test, and the operation of the package after it is mounted. And, if moisture infiltrates into the delamination, cracks can occur in the molded body 8 of the package, which causes many problems, such as a drop in production yield, and package defects during use of the package after mounting it on a board which leads to replacement of the package.